Abstract
The main technical challenge of the medium-voltage motor drives with modular multilevel converter (MMC) is the serious low-frequency fluctuation on the capacitor voltages, and the existing suppression methods inevitably inject high-frequency circulating currents in MMC. However, the output currents are evidently distorted by the large injected components, while little research has been done to study and solve this problem. This paper analyzes and proves the essential interactions between the output current distortion and the injected components, and the specific dominant output harmonic groups are derived and summarized, revealing the nature of the problem, and it can be taken as a favorable reference for the controller designing. Based on the derivations, this paper proposes a novel suppression method for the greatly improved harmonic characteristics of the output currents during the low-frequency operation. The output harmonics can be accurately measured by the proposed control and effectively suppressed for much lower current total harmonic distortion, benefiting for the superior output control performances with improved efficiency. The simulation results on PSCAD/EMTDC and experimental verifications on a 2.2 kW MMC-based motor drive prototype prove the validity of the presented harmonic analysis and suppression method.
| Original language | English |
|---|---|
| Article number | 8703842 |
| Journal | IEEE Transactions on Power Electronics |
| Volume | 35 |
| Issue number | 1 |
| Pages (from-to) | 744-759 |
| Number of pages | 16 |
| ISSN | 0885-8993 |
| DOIs | |
| Publication status | Published - Jan 2020 |
| Externally published | Yes |
Bibliographical note
Funding Information:Manuscript received November 4, 2018; revised February 6, 2019 and April 9, 2019; accepted April 22, 2019. Date of publication April 30, 2019; date of current version October 18, 2019. This work was supported by the National Natural Science Foundation of China under Project 51277146. Recommended for publication by Associate Editor N. R. Zargari. (Corresponding author: Fangzhou Zhao.) F. Zhao, G. Xiao, T. Zhu, X. Zheng, and Z. Wu are with the State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China (e-mail:,zfzhaha @stu.xjtu.edu.cn; xgc@mail.xjtu.edu.cn; zth1222@163.com; zhengxu201706 @stu.xjtu.edu.cn; wzq342910214@stu.xjtu.edu.cn).
Publisher Copyright:
© 2019 IEEE.
Keywords
- Harmonic analysis and suppression
- low-frequency fluctuation
- modular multilevel converter (MMC)
- motor drives